September 24, 2010

Welcome to the Age of Seawalls

Over on the main site, Steve Nash has a great piece about how cities in the United States are preparing for sea-level rise. The picture's pretty bleak. Most states and localities aren't doing much planning at all. And when they are taking action, they're actually making things worse. Here's a snippet:

There are three broad options for dealing with sea-level rise. We can build walls to ward off the sea. We can put our coastal buildings and infrastructure up on stilts. Or we can plan a slow retreat and move our built environment farther inland. All of these options would take a long time to implement, and many of them would be absurdly expensive. Jim Titus, chief sea-level-rise expert at the Environmental Protection Agency (EPA), estimates that shore protection for the lower 48 states could cost around $1 trillion.

And seawalls—a necessity to protect places like Manhattan—could create as many problems as they solve. Dikes, levees, and bulkheads will destroy many coastal wetlands by preventing them from migrating inland as the seas advance. Most of the coastal wetlands in the mid-Atlantic could disappear by the end of the century if they have no place to go and the seas rise three feet or more. These wetlands are highly valuable, reducing the impact of floods, protecting against storms, and shielding freshwater supplies from the ocean. They’re also key nurseries for fish: About two-thirds of the commercial fisheries off the Atlantic depend on wetlands, where invertebrates and small fish that feed on decomposing matter support rockfish, menhaden, blue crab, and other large species.